THROUGH, THOROUGH and THREW

Through is a preposition which can make a phrase with a noun: through the window.
Thorough means in detail, complete, with care. His work was always thorough.

A good way to remember is that thorough is a longer word and it suggests taking a long time over something.

Threw is the past tense of throw. She threw the jewel across the room.  Remember this sentence and the two ew syllables.